Yes, the method works with all brass cartridges, including rimless. I didn't mention using it with magnum revolver or rifle cases because with those guns sticky brass, or slight extraction is normally considered maximum safe pressure, if the load is backed off a little till extraction is smooth and effortless.
As I explained in my book, with rimless cases, hold your mike in contact with the rim when taking your measurement, and measure the swell at its largest point. With rimless cases, measure the swell at the largest point, or, in other words record the largest reading you can get off the case.
For those of you who don't have me book, the method is as follows.
1. Fire a cylinder full of a known load. If wanting to duplicate +P pressure in a 38, use factory rounds. In magnum revolvers, or non magnum, use the hottest loads you can buy, which will probably be a heavy bullet load. If working with a rifle case, or rimless, 5 shots would be a good number, again using a factory round. Do your measuring to 4 decimal places, i.e. .0002, commonly known among machinests as tenths of a thousandth, or ten thousandths.
2. Add up all the measurements then divide by the number of cases measured but carry this measurement to 5 places. ( .00000) This will be your pressure standard.
3. Useing the same brass, WITH ANY POWDER , PRIMER, OR BULLET COMBINATION YOU WANT TO USE, and work up loads to the same expansion measurement. When working up loads it will be difficult to match the average, so stay a little under and be safe. The key to accuracy here is to use the same brass, and it must not be work hardened too much from repeated firings or more pressure will be required to reach the pressure standard diameter. The solution is , after working up a load, test the results with brass from a new set of fired factory laods .
This pressure measuring method is so precise that a powder change of only one tenth of a grain in 38 special brass will give a very measurable diameter incease. Compare that to the fact that a half grain, or 5 tenths of a grain powder change will not take a full load in a small case, using the fastest powders, into a pressure danger.
